I’m a newbie too, but strikes me the more you measure the more fluctuation you will see. I measured mine at the start and at the finish and had only two readings. I also suspect you are finding the wine is disappearing, have a word with your wife and ask her to stop sampling ;) seriously though...
1st fermentation’s completed this is the Ph as I enter it into the 2nd fermentation. I believe I could add a wine with higher Ph, water, or sugar I suppose.